The basal ganglia (BG) are involved in the control of axial, proximal and distal muscles. While the role of the BG in proximal/distal muscle activities has been heavily investigated, the involvement in axial movements has received much less attention. The broad objective of the research described in this proposal is to begin a program of research that is focussed on assessing the BG's role in axial muscle control. It can be stated with some certainty that the BG affect movement, in general, by influencing other motor areas. Since the reticular formation (RF) is critical for axial muscle control, the present research will focus on BG-RF interactions. For these experiments, neural activity will be painlessly recorded from behaving cats. These studies have the following Specific Aims: 1. Assess the role of direct and indirect BG influences on the RF. 2. Determine whether BG influences are exerted tonically or phasically. 3. Determine the way in which BG influences on the RF are translated into effects on movement. Findings from this research are relevant to understanding the dyskinesias that invariably follow BG pathology in humans. For example, Parkinson's disease, Wilson's disease and Huntington's Chorea all include profound disruption of axial muscle activities among their motor sequelae. Elucidation of the way in which a normal BG controls such movements is an important prerequisite for the eventual development of treatment modalities for a dysfunctional BG.